The present invention relates to improvements in a drilling direction control device.
Directional drilling involves varying or controlling the direction of a wellbore as it is being drilled. Usually the goal of directional drilling is to reach or maintain a position within a target subterranean destination or formation with the drilling string. For instance, the drilling direction may be controlled to direct the wellbore towards a desired target destination, to control the wellbore horizontally to maintain it within a desired payzone or to correct for unwanted or undesired deviations from a desired or predetermined path.
Thus, directional drilling may be defined as deflection of a wellbore along a predetermined or desired path in order to reach or intersect with, or to maintain a position within, a specific subterranean formation or target. The predetermined path typically includes a depth where initial deflection occurs and a schedule of desired deviation angles and directions over the remainder of the wellbore. Thus, deflection is a change in the direction of the wellbore from the current wellbore path. This deflection may pertain to deviation of the wellbore path relative to vertical or to change in the horizontal direction or azimuth of the wellbore path.
It is often necessary to adjust the direction of the wellbore frequently while directional drilling, either to accommodate a planned change in direction or to compensate for unintended or unwanted deflection of the wellbore. Unwanted deflection may result from a variety of factors, including the characteristics of the formation being drilled, the makeup of the bottomhole drilling assembly and the manner in which the wellbore is being drilled.
Deflection is measured as an amount of deviation of the wellbore from the current wellbore path and is expressed as a deviation angle or hole angle. Deflection may also relate to a change in the azimuth of the wellbore path. Commonly, the initial wellbore path is in a vertical direction. Thus, initial deflection often signifies a point at which the wellbore has deflected off vertical in a particular azimuthal direction. Deviation is commonly expressed as an angle in degrees from the vertical. Azimuth is commonly expressed as an angle in degrees relative to north.
Various techniques may be used for directional drilling. First, the drilling bit may be rotated by a downhole motor which is powered by the circulation of fluid supplied from the surface. This technique, sometimes called xe2x80x9csliding drillingxe2x80x9d, is typically used in directional drilling to effect a change in direction of the a wellbore, such as the building of an angle of deflection. However, various problems are often encountered with sliding drilling.
For instance, sliding drilling typically involves the use of specialized equipment in addition to the downhole drilling motor, including bent subs or motor housings, steering tools and nonmagnetic drill string components. As well, the downhole motor tends to be subject to wear given the traditional, elastomer motor power section. Furthermore, since the drilling string is not rotated during sliding drilling, it is prone to sticking in the wellbore, particularly as the angle of deflection of the wellbore from the vertical increases, resulting in reduced rates of penetration of the drilling bit. Other traditional problems related to sliding drilling include stick-slip, whirling, differential sticking and drag problems. For these reasons, and due to the relatively high cost of sliding drilling, this technique is not typically used in directional drilling except where a change in direction is to be effected.
Second, directional drilling may be accomplished by rotating the entire drilling string from the surface, which in turn rotates a drilling bit connected to the end of the drilling string. More specifically, in rotary drilling, the bottomhole assembly, including the drilling bit, is connected to the drilling string which is rotatably driven from the surface. This technique is relatively inexpensive because the use of specialized equipment such as downhole drilling motors can usually be kept to a minimum. In addition, traditional problems related to sliding drilling, as discussed above, are often reduced. The rate of penetration of the drilling bit tends to be greater, while the wear of the drilling bit and casing are often reduced.
However, rotary drilling tends to provide relatively limited control over the direction or orientation of the resulting wellbore as compared to sliding drilling, particularly in extended-reach wells. Thus rotary drilling has tended to be largely used for non-directional drilling or directional drilling where no change in direction is required or intended.
Third, a combination of rotary and sliding drilling may be performed. Rotary drilling will typically be performed until such time that a variation or change in the direction of the wellbore is desired. The rotation of the drilling string is typically stopped and sliding drilling, through use of the downhole motor, is commenced. Although the use of a combination of sliding and rotary drilling may permit satisfactory control over the direction of the wellbore, the problems and disadvantages associated with sliding drilling are still encountered.
Some attempts have been made in the prior art to address these problems. Specifically, attempts have been made to provide a steerable rotary drilling apparatus or system for use in directional drilling. However, none of these attempts have provided a fully satisfactory solution.
United Kingdom Patent No. GB 2,172,324 issued Jul. 20, 1988 to Cambridge Radiation Technology Limited (xe2x80x9cCambridgexe2x80x9d) utilizes a control module comprising a casing having a bearing at each end thereof for supporting the drive shaft as it passes through the casing. Further, the control module is comprised of four flexible enclosures in the form of bags located in the annular space between the drilling string and the casing to serve as an actuator. The bags actuate or control the direction of drilling by applying a radial force to the drive shaft within the casing such that the drive shaft is displaced laterally between the bearings to provide a desired curvature of the drive shaft. Specifically, hydraulic fluid is selectively conducted to the bags by a pump to apply the desired radial force to the drilling string.
Thus, the direction of the radial force applied by the bags to deflect the drive shaft is controlled by controlling the application of the hydraulic pressure from the pump to the bags. Specifically, one or two adjacent bags are individually fully pressurized and the two remaining bags are depressurized. As a result, the drive shaft is deflected and produces a curvature between the bearings at the opposing ends of the casing of the control module. This controlled curvature controls the drilling direction.
United Kingdom Patent No. GB 2,172,325 issued Jul. 20, 1988 to Cambridge and United Kingdom Patent No. GB 2,177,738 issued Aug. 3, 1988 to Cambridge describe the use of flexible enclosures in the form of bags in a similar manner to accomplish the same purpose. Specifically, the drilling string is supported between a near bit stabilizer and a far bit stabilizer. A control stabilizer is located between the near and far bit stabilizers for applying a radial force to the drilling string within the control stabilizer such that a bend or curvature of the drilling suing is produced between the near bit stabilizer and the far bit stabilizer. The control stabilizer is comprised of four bags located in the annular space between a housing of the control stabilizer and the drilling string for applying the radial force to the drilling string within the control stabilizer.
United Kingdom Patent Application No. GB 2,307,537 published May 28, 1997 by Astec Developments Limited describes a shaft alignment system for controlling the direction of rotary drilling. Specifically, a shaft, such as a drilling string, passes though a first shaft support means having a first longitudinal axis and a second shaft support means having a second longitudinal axis. The first and second shaft support means are rotatably coupled by bearing means having a bearing rotation axis aligned at a first non-zero angle with respect to the first longitudinal axis and aligned at a second non-zero angle with respect to the second longitudinal axis. As a result, relative rotation of the first and second shaft support means about their respective longitudinal axes varies the relative angular alignment of the first and second longitudinal axes.
The shaft passing through the shaft alignment system is thus caused to bend or curve in accordance with the relative angular alignment of the first and second longitudinal axes of the first and second shaft support means. The shaft may be formed as a unitary item with a flexible central section able to accommodate the desired curvature or it may be comprised of a coupling, such as a universal joint, to accommodate the desired curvature.
U.S. Pat. No. 5,685,379 issued Nov. 11, 1997 to Barr et. at. U.S. Pat. No. 5,706,905 issued Jan. 13, 1998 to Barr et. at. and U.S. Pat. No. 5,803,185 issued Sep. 8, 1998 to Barr et. al. describe a steerable rotary drilling system including a modulated bias unit, associated with the drilling bit, for applying a lateral bias to the drilling bit in a desired direction to control the direction of drilling. The bias unit is comprised of three equally spaced hydraulic actuators, each having a movable thrust member which is displaceable outwardly for engagement with the wellbore. The hydraulic actuators are operated in succession as the bias unit rotates during rotary drilling, each in the same rotational position, so as to displace the bias unit laterally in a selected direction.
PCT International Application No. PCT/US98/24012 published May 20, 1999 as No. WO 99/24688 by Telejet Technologies, Inc. describes the use of a stabilizer assembly for directional drilling. More particularly, a stabilizer sub is connected with the rotary drilling string such that the stabilizer sub remains substantially stationary relative to the wellbore as the drilling string rotates. The stabilizer sub includes a fixed upper stabilizer and an adjustable lower stabilizer. The lower adjustable stabilizer carries at least four stabilizer blades which are independently radially extendable from the body of the stabilizer sub for engagement with the wellbore.
Each stabilizer blade is actuated by a motor associated with each blade, which extends and retracts the blade through longitudinal movement of the stabilizer body relative to the stabilizer blade. Because each stabilizer blade is provided with its own motor, the stabilizer blades are independently extendable and retractable with respect to the body of the stabilizer sub. Accordingly, each blade may be selectively extended or retracted to provide for the desired drilling direction.
U.S. Pat. No. 5,307,885 issued May 3, 1994 to Kuwana et. al., U.S. Pat. No. 5,353,884 issued Oct. 11, 1994 to Misawa et. al. and U.S. Pat. No. 5,875,859 issued Mar. 2, 1999 to Ikeda et. al. all utilize harmonic drive mechanisms to drive rotational members supporting the drilling string eccentrically to deflect the drilling string and control the drilling direction.
More particularly, Kuwana et. al. describes a first rotational annular member connected with a first harmonic drive mechanism a spaced distance from a second rotational annular member connected with a second harmonic drive mechanism. Each rotational annular member has an eccentric hollow portion which rotates eccentrically round the rotational axis of the annular member. The drilling string is supported by the inner surfaces of the eccentric portions of the annular members. Upon rotation by the harmonic drive mechanisms, the eccentric hollow portions are rotated relative to each other in order to deflect the drilling string and change the orientation of the drilling sting to the desired direction. Specifically, the orientation of the drilling sting is defined by a straight line passing through the centres of the respective hollow portions of the annular members.
Misawa et. al. describes harmonic drive mechanisms for driving first and second rotatable annular members of a double eccentric mechanism. The first rotatable annular member defines a first eccentric inner circumferential surface. The second rotatable annular member, rotatably supported by the first eccentric inner circumferential surface of the first annular member, defines a second eccentric inner circumferential surface. The drilling string is supported by the second eccentric inner circumferential surface of the second annular member and uphole by a shaft retaining mechanism. Thus, upon actuation of the harmonic drive mechanisms, the first and second annular members are rotated resulting in the movement of the center of the second eccentric circumferential surface. Thus the drilling string is deflected from its rotational centre in order to orient it in the desired direction.
Upon deflection of the drilling string, the fulcrum point of the deflection of the drilling string tends to be located at the upper supporting mechanism, i.e. the upper shaft retaining mechanism. As a result, it has been found that the drilling string may be exposed to excessive bending stress.
Similarly, Ikeda et. al. describes harmonic drive mechanisms for driving first and second rotatable annular members of a double eccentric mechanism. However, Ikeda et al. requires the use of a flexible joint, such as a universal joint, to be connected into the drilling string at the location at which the maximum bending stress on the drilling string takes place in order to prevent excessive bending stress on the drilling string. Thus, the flexible joint is located adjacent the upper supporting mechanism. Upon deflection of the drilling string by the double eccentric mechanism, the deflection is absorbed by the flexible joint and thus a bending force is not generated on the drilling string. Rather, the drilling string is caused to tilt downhole of the double eccentric mechanism. A fulcrum bearing downhole of the double eccentric mechanism functions as a thrust bearing and serves as a rotating centre for the lower portion of the drilling string to accommodate the tilting action.
However, it has been found that the use of a flexible or articulated shaft to avoid the generation of excessive bending force on the drilling string may not be preferred. Specifically, it has been found that the articulations of the flexible or articulated shaft may be prone to failure.
Canadian Patent Application No. 2,298,375 by Schlumberger Canada Limited laid-open on Sep. 15, 2000, describes a rotary steerable drilling system which includes a pivoting offsetting mandrel which is supported within a tool collar by a knuckle joint and which in turn supports a drilling bit. The angular position of to offsetting mandrel is controlled by an arrangement of hydraulic pistons which are disposed between the offsetting mandrel and to tool collar and which can be selectively extended and retracted to move the offsetting mandrel relative to the tool collar. This system is therefore somewhat complicated, requiring the use of the articulating knuckle joint and a plurality of independently actuatable hydraulic pistons.
U.S. Pat. No. 6,244,361 Dl issued Jun. 12, 2001 to Halliburton Energy Services, Inc. describes a drilling direction control device which includes a rotatable drilling shaft, a housing for rotatably supporting the drilling shaft, and a deflection assembly. The deflection assembly includes an eccentric outer ring and an eccentric inner ring which can be selectively rotated to bend the drilling shaft in various directions. The deflection assembly is actuated by a harmonic drive system, which is a relatively complex and expensive apparatus to construct and maintain.
As a result, there remains a need in the industry for a relatively simple and economical steerable rotary drilling device or drilling direction control device for use with a rotary drilling string which can provide relatively accurate control over the trajectory or orientation of the drilling bit during the drilling operation, while also avoiding the generation of excessive bending stress on the drilling string.
There is also a need for such a drilling direction control device which is adaptable for use in a relatively small diameter embodiment.
The present invention is directed at improvements in a drilling direction control device of the general type described in U.S. Pat. No. 6,244,361 B1 (Halliburton Energy Services, Inc.), comprising:
(a) a rotatable drilling shaft;
(b) a housing for rotatably supporting a length of the drilling shaft for rotation therein; and
(c) a drilling shaft deflection assembly contained within the housing and axially located between a first support location and a second support location, for bending the drilling shaft between the first support location and the second support location.
The contents of U.S. Pat. No. 6,244,361 B1 are hereby incorporated by reference into this Specification.
In particular, the invention is comprised of a drilling shaft deflection assembly for use in a drilling direction control device of the type described above. The invention may also be comprised of an indexing assembly, a housing locking assembly and a housing orientation sensor apparatus.
The function of the drilling shaft deflection assembly is to create a bend in the drilling shaft. The function of the indexing assembly is to orient the bend in the drilling shaft to provide a desired toolface orientation. The function of the housing locking assembly is to selectively engage the housing with the drilling shaft so that the housing and the drilling shaft rotate together. The function of the housing orientation sensor apparatus is to provide a relatively simple apparatus for sensing the orientation of the housing relative to some reference orientation.
In one apparatus aspect of the invention, the invention is comprised of a drilling shaft deflection assembly for a drilling direction control device of the type comprising a rotatable drilling shaft and a housing for rotatably supporting a length of the drilling shaft for rotation therein, wherein the drilling shaft deflection assembly is contained within the housing and is axially located between a first support location and a second support location, for bending the drilling shaft between the first support location and the second support location, and wherein the deflection assembly comprises:
(a) a deflection mechanism for imparting lateral movement to the drilling shaft in order to bend the drilling shaft;
(b) a deflection actuator for actuating the deflection mechanism in response to longitudinal movement of the deflection actuator; and
(c) a deflection linkage mechanism between the deflection mechanism and the deflection actuator for converting longitudinal movement of the deflection actuator to lateral movement of the drilling shaft.
The drilling shaft deflection assembly as described above may encompass a variety of embodiments. The essence of the drilling shaft deflection assembly in all of the embodiments of the invention is the use of the longitudinally movable deflection actuator to effect lateral movement of the drilling shaft via the deflection linkage mechanism.
The drilling direction control device as described above may be further comprised of an indexing assembly for orienting the bend in the drilling shaft. Where an indexing assembly is provided, it may be integrated with the drilling shaft deflection assembly or it may be comprised of a separate apparatus.
The drilling direction control device as described above may be further comprised of a housing locking assembly for selectively engaging the housing with the drilling shaft so that they rotate together.
The drilling direction control device as described above may be further comprised of a housing orientation sensor apparatus for sensing the orientation of the housing.
The drilling shaft deflection assembly may be comprised of any structure or apparatus which includes a deflection mechanism for imparting lateral movement to the drilling shaft, a longitudinally movable deflection actuator for actuating the deflection mechanism, and a deflection linkage mechanism for converting longitudinal movement of the deflection actuator to lateral movement of the drilling shaft.
The deflection mechanism may be comprised of any structure or apparatus which is movable within the housing to impart lateral movement to the drilling shaft to bend the drilling shaft. The deflection mechanism may be movable by translation or by rotation, and may be movable in a plane which is either parallel with or perpendicular to the longitudinal axis of the drilling shaft.
The deflection actuator may be comprised of any structure or apparatus which is longitudinally movable within the housing to actuate the deflection mechanism and which is compatible with the deflection mechanism.
The deflection actuator is preferably further comprised of a power source for effecting longitudinal movement of the deflection actuator. The power source may be comprised of any structure or apparatus which can effect longitudinal movement of the deflection actuator.
For example, the power source may be comprised of hydraulic pressure exerted directly on the deflection actuator by drilling fluid being passed through the drilling direction control device. Preferably the power source is comprised of a hydraulic system contained within the housing. Preferably the hydraulic system is comprised of an annular pump which is driven by rotation of the drilling shaft. Preferably the hydraulic fluid is comprised of an oil. Preferably the hydraulic system is also comprised of a reciprocating hydraulic piston in a cylinder. Preferably the hydraulic system is double acting so that the power source operates to effect longitudinal movement of the deflection actuator in two directions. Preferably the annular pump is a gear pump which is driven by rotation of the drilling shaft.
The deflection linkage mechanism may be comprised of any structure or apparatus which is capable of converting longitudinal movement of the deflection actuator to lateral movement of the drilling shaft. As a result, the deflection linkage mechanism must be compatible with both the deflection mechanism and the deflection actuator.
In a first preferred embodiment of drilling shaft deflection assembly, the deflection mechanism may be comprised of an outer ring which is rotatably supported on a circular inner peripheral surface within the housing and which has a circular inner peripheral surface which is eccentric with respect to the housing, and an inner ring which is rotatably supported on the circular inner peripheral surface of the outer ring and which has a circular inner peripheral surface which engages the drilling shaft and which is eccentric with respect to the circular inner peripheral surface of the outer ring. The outer ring and the inner ring are capable of rotation relative to each other in a plane which is perpendicular to the longitudinal axis of the drilling shaft in order to impart lateral movement to the drilling shaft. Preferably the outer ring and the inner ring are both rotatable relative to the housing but are not movable longitudinally to any material extent.
In the first preferred embodiment of drilling shaft deflection assembly, the deflection actuator is comprised of a longitudinally movable cam device.
In the first preferred embodiment of drilling shaft deflection assembly the deflection linkage mechanism is comprised of a first track associated with the cam device for engaging a first deflection linkage member and a second track associated with the cam device for engaging a second deflection linkage member, both through complementary engagement surfaces. At least one of the first track and the second track is a spiral track so that the deflection linkage members will rotate relative to each other upon longitudinal movement of the cam device. Preferably the first track and the second track are opposing spiral tracks so that the deflection linkage members will rotate in opposite directions upon longitudinal movement of the cam device.
In the first preferred embodiment of drilling shaft deflection assembly, the cam device is comprised of a tubular sleeve cam which reciprocates within the housing, and the first deflection linkage member and the second deflection linkage member are both telescopically and rotatably received within the sleeve cam.
In the first preferred embodiment of drilling shaft deflection assembly, the deflection linkage mechanism is further comprised of the first deflection linkage member and the second deflection linkage member. The first deflection linkage member is connected with the outer ring and the second deflection linkage member is connected with the inner ring so that rotation of the first and second deflection linkage members will result in rotation of the outer ring and the inner ring respectively.
In a second preferred embodiment of drilling shaft deflection assembly the deflection mechanism is comprised of a camming surface associated with an inner surface of the housing and a follower member which is laterally movable between the housing and the drilling shaft. The camming surface and the follower member take the place of the outer ring and the inner ring of the first preferred embodiment. The camming surface and the follower member are capable of rotation relative to each other in a plane which is perpendicular to the longitudinal axis of the drilling shaft so that lateral movement of the follower member caused by the camming surface results in lateral movement of the drilling shaft. Preferably neither the camming surface nor the follower member is movable longitudinally to any material extent.
In the second preferred embodiment of the drilling shaft deflection assembly, as in the first preferred embodiment, the deflection actuator is comprised of a longitudinally movable rotary cam device.
In the second preferred embodiment of drilling shaft deflection assembly, the deflection linkage mechanism is comprised of a first track associated with the cam device for engaging a first deflection linkage member and may be comprised of a second track associated with the cam device for engaging a second deflection linkage member, both through complementary engagement surfaces. At least one of the first track and the second track is a spiral track so that the linkage members will rotate relative to each other upon longitudinal movement of the cam device.
In the second preferred embodiment of drilling shaft deflection assembly, the cam device is comprised of a tubular sleeve cam which reciprocates within the housing, and the deflection linkage member or members are telescopically and rotatably received within the sleeve cam.
In the second preferred embodiment of drilling shaft deflection assembly, the deflection linkage mechanism is further comprised of the deflection linkage member or members. The first deflection linkage member may be connected with one of the camming surface and the follower member and the second deflection linkage member may be connected with the other of the camming surface and the follower member so that rotation of the first and second deflection linkage members will result in relative rotation of the camming surface and the follower member.
In the second preferred embodiment of drilling shaft deflection assembly, the position of the camming surface will determine the orientation of the bend in the drilling shaft, while the relative positions of the camming surface and the follower member will determine the magnitude of the drilling shaft deflection. The deflection mechanism may therefore be actuated by rotation of the camming surface and the follower member relative to each other, while indexing of the deflection mechanism to attain a desired toolface orientation may be achieved by coordinated rotation together of the camming surface and the follower member. As a result, the second track and the second deflection linkage member may be omitted if the sole function of the deflection assembly is to deflect the drilling shaft without providing an indexing function.
In a third preferred embodiment of drilling shaft deflection assembly, the deflection mechanism is comprised of at least one laterally movable follower member which is disposed between the housing and the drilling shaft. Preferably the deflection mechanism is comprised of either a plurality of follower members or a single follower member with a plurality of follower member surfaces for engaging a plurality of camming surfaces. The follower member and the follower member surfaces may be of any shape and configuration which is compatible with the deflection actuator. The follower member engages the drilling shaft either directly or indirectly so that lateral movement of the follower member results in lateral movement of the drilling shaft.
In the third preferred embodiment of drilling shaft deflection assembly, the deflection linkage mechanism is comprised of at least one camming surface associated with the deflection actuator which engages the follower member in order to convert longitudinal movement of the deflection actuator to lateral movement of the follower member between the housing and the drilling shaft. Preferably the camming surface is longitudinally movable by the deflection actuator and preferably the follower member is not capable of longitudinal movement to any material extent. Preferably the follower member or members and their associated camming surfaces are comprised of complementary ramp surfaces.
Preferably the deflection actuator is comprised of a deflection actuator member and a power source for the deflection actuator. The deflection actuator member may be comprised of any longitudinally movable member. For example, the deflection actuator is preferably comprised of a hydraulic system and the deflection actuator member is preferably comprised of a reciprocating rod which is connected with both the camming surface and a hydraulic piston which is a component of the hydraulic system, so that reciprocation of the piston within a hydraulic cylinder results in reciprocation of the deflection actuator member and the camming surface.
In the third preferred embodiment of drilling shaft deflection assembly, the deflection assembly may impart lateral movement to the drilling shaft along a single axis or along a plurality of axes.
For uni-axial bending of the drilling shaft, the deflection assembly may be comprised of a single follower member and associated camming surface, or may be comprised of one or more follower members and associated camming surfaces which are separated by 180 degrees around the drilling shaft, thus providing additional support for the drilling shaft as it is being bent. Where a single follower member is used with a plurality of camming surfaces, the follower member preferably includes a plurality of follower member surfaces.
For multi-axial bending of the drilling shaft, the deflection assembly may be comprised of multiple deflection assemblies as described above for uni-axial bending, in which the multiple deflection assemblies are spaced radially about the drilling shaft. Preferably, the deflection assemblies are evenly spaced about the drilling shaft so that in the case of bi-axial bending the deflection assemblies are separated by about 90 degrees.
The multiple deflection assemblies may include a single follower member with a plurality of follower member surfaces or may include a plurality of follower members. Most preferably the deflection assembly is comprised of a single follower member with a plurality of follower member surfaces in the case of both uni-axial and multi-axial bending of the drilling shaft.
In the case of multi-axial bending of the drilling shaft, the follower member, the follower member surfaces and the camming surfaces preferably accommodate forced lateral movement of the follower member which results from movement of the follower member in more than one plane. Preferably this forced lateral movement is accommodated by allowing for movement of the camming surfaces relative to the follower member surfaces which is not parallel to the direction of movement required to actuate the deflection mechanism.
The drilling direction control device preferably includes an indexing assembly for orienting the bend in the drilling shaft so that the device may be used to provide directional control during drilling operations. The indexing assembly may be integrated with the drilling shaft deflection assembly or it may be comprised of a separate apparatus.
For example, the indexing assembly may be comprised of providing the deflection mechanism with the capability of bending the drilling shaft in a controlled manner in a plurality of directions (i.e., biaxial or multiaxial bending of the drilling shaft such as, for example, that provided by the drilling shaft deflection assembly described in U.S. Pat. No. 6,244,361 (Halliburton Energy Services. Inc.)).
Alternatively, the indexing assembly may be comprised of an apparatus for orienting a bend in the drilling shaft (i.e., the toolface) by rotating one or both of the deflection mechanism and the housing. If the deflection mechanism has a fixed orientation relative to the housing, then the bend may be oriented by rotating both of the deflection mechanism and the housing, since they will rotate together. If the deflection mechanism and the housing do not have a fixed orientation relative to each other, then the bend must be oriented by rotating the deflection mechanism. In either case, the indexing assembly may utilize components of the deflection assembly or it may be independent of the deflection assembly.
Preferably the indexing assembly is comprised of an indexing mechanism for imparting rotational movement to the deflection mechanism, an indexing actuator for actuating the indexing mechanism in response to longitudinal movement of the indexing actuator, and an indexing linkage mechanism between the indexing mechanism and the indexing actuator for converting longitudinal movement of the indexing actuator to rotational movement of the deflection mechanism.
The indexing mechanism may be comprised of any structure or apparatus which is capable of imparting rotation to the deflection mechanism. The indexing actuator may be comprised of any longitudinally movable structure or apparatus which is capable of actuating the indexing mechanism through the indexing linkage mechanism. The indexing linkage mechanism may be comprised of any structure or apparatus which is capable of converting the longitudinal movement of the indexing actuator to rotational movement of the deflection mechanism.
The indexing actuator is preferably further comprised of a power source. The power source may be comprised of the flow of drilling fluid through the drilling direction control device. Preferably, however, the indexing actuator is comprised of an independent power source, such as a pump, a motor, or a pump/motor combination. Preferably the power source is comprised of a hydraulic system. Preferably the hydraulic system includes a reciprocating hydraulic piston in a cylinder. Preferably the hydraulic system further comprises a hydraulic pump for supplying hydraulic fluid to the cylinder. Preferably the hydraulic system is double acting so that the indexing actuator can be driven in two directions. The hydraulic pump may be powered by any suitable motor or device. Preferably the hydraulic pump is powered by the rotation of the drilling shaft. Preferably the hydraulic pump is an annular pump such as a gear pump. The power source for the indexing assembly may be the same power source that powers the deflection assembly or it may be a separate power source.
In a first preferred embodiment of indexing assembly, the indexing assembly is comprised of an apparatus similar to that utilized in the Sperry-Sun Drilling Services Coiled Tubing BHA Orienter. The Sperry-Sun Drilling Services Coiled Tubing BHA Orienter is described in a Technology Update published by Sperry-Sun Drilling Services in Winter 1995, which Technology Update is hereby incorporated by reference into this Specification.
Specifically, in the first preferred embodiment of indexing assembly, the indexing mechanism is comprised of a ratchet mechanism which selectively interlocks the deflection mechanism and the indexing linkage mechanism for rotation of the deflection mechanism in a single direction, the indexing actuator is comprised of a longitudinally movable piston, and the indexing linkage mechanism is comprised of a barrel cam device which converts longitudinal movement of the piston to rotation of the deflection mechanism.
In the first preferred embodiment of indexing assembly, the indexing linkage mechanism is further comprised of a helical groove in the barrel cam and a pin on the housing which engages the helical groove so that the barrel cam will rotate relative to the housing as the pin travels the length of the helical groove.
In the first preferred embodiment of indexing assembly, the indexing actuator is further comprised of a hydraulic system as a power source. Preferably the hydraulic system includes a reciprocating hydraulic piston in a cylinder. Preferably the hydraulic system further comprises a hydraulic pump for supplying hydraulic fluid to the cylinder. Preferably the hydraulic pump is powered by the rotation of the drilling shaft. Preferably the hydraulic system is double acting. The power source for the indexing assembly may be the same power source that powers the deflection assembly or it may be a separate power source.
The first preferred embodiment of indexing assembly may be easily adapted for use with any of the embodiments of deflection assembly. A second preferred embodiment of indexing assembly is intended for use specifically with the first and second preferred embodiments of deflection assembly, since it is integrated with the first and second preferred embodiments of deflection assembly.
In the second preferred embodiment of indexing assembly, the indexing mechanism is comprised of components of the deflection mechanism of either the first or second preferred embodiment of deflection assembly, the indexing actuator is comprised of components of the deflection actuator of either the first or second preferred embodiment of deflection assembly, and the indexing linkage mechanism is comprised of components of the deflection linkage mechanism of either the first or second embodiment of deflection assembly.
In the second preferred embodiment of indexing assembly, once the drilling shaft has been bent by the deflection assembly, simultaneous rotation of the deflection assembly as a unit will serve to orient the direction of the bend in the drilling shaft. This result is achieved by designing the tracks in the cam device which comprise the indexing linkage mechanism so that the indexing linkage mechanism will rotate the entire deflection mechanism at the same rate in response to longitudinal movement of the deflection actuator.
This result may in turn be achieved by designing the tracks in the cam device in two contiguous segments. A deflection segment of the tracks is utilized for bending of the drilling shaft while an indexing segment of the tracks is utilized for orientation of the bend in the drilling shaft. In the deflection segment the deflection linkage mechanism causes the components of the deflection mechanism to rotate at different rates and/or in different directions, while in the indexing segment the indexing linkage mechanism causes the components of the deflection mechanism to rotate together at the same rate and in the same direction.
In a third embodiment of indexing assembly, the deflection assembly facilitates multi-axial deflection of the drilling shaft and the indexing assembly is a component of the deflection assembly. The indexing assembly utilizes the multi-axial deflection of the drilling shaft to control the orientation of the bend in the drilling shaft.
For example, the indexing assembly could be comprised of the deflection assembly of either the first or second preferred embodiments of deflection assembly in which case the components of the deflection mechanism could be rotated independently to achieve both a desired deflection and a desired orientation of the bend in the drilling shaft.
A description of the manner in which the outer ring and the inner ring of the first preferred embodiment of deflection assembly could be rotated to achieve this result may be found in U.S. Pat. No. 6,244,361 B1. This system could easily be modified for use with the second preferred embodiment of deflection assembly.
As another example, the indexing assembly could be comprised of the deflection assembly of the third embodiment of deflection assembly in which multi-axial deflection is facilitated. In this case, selective deflection of the drilling shaft along more than one axis can be used to achieve a desired deflection and a desired orientation of the bend in the drilling shaft.
The third embodiment of indexing assembly is relatively complex, since it requires simultaneous deflection and indexing via the same apparatus. As a result, the third embodiment of indexing assembly is not preferred in circumstances where a relatively simple design for the drilling direction control device is desired.
The indexing assembly is preferably actuated with reference to the orientation of the housing. As a result, the drilling direction control device is preferably further comprised of a housing orientation sensor apparatus associated with the housing for sensing the orientation of the housing.
The housing orientation sensor apparatus may sense the orientation of the housing in three dimensions in space and may be comprised of any apparatus which is capable of providing this sensing function and the desired accuracy in sensing. The housing orientation sensor apparatus may therefore be comprised of one or more magnetometers, accelerometers or a combination of both types of sensing apparatus.
Alternatively, the housing orientation sensor apparatus may be designed more simply to sense the orientation of the housing relative only to gravity. In other words, the housing orientation sensor apparatus may be designed to sense only the orientation of the housing relative to the xe2x80x9chigh sidexe2x80x9d or the xe2x80x9clow sidexe2x80x9d of the wellbore being drilled. In this case, the housing orientation sensor apparatus may be comprised of any gravity sensor or combination of gravity sensors, such as an accelerometer, a plumb bob or a rolling ball in a track.
Alternatively, the housing orientation sensor apparatus may be designed to sense the orientation of the housing relative only to the earth""s magnetic field. In other words, the housing orientation sensor apparatus may be designed to sense only the orientation of the housing relative to magnetic north. In this case, the housing orientation sensor apparatus may be comprised of any magnetic sensor or combination of magnetic sensors, such as a magnetometer.
The housing orientation sensing apparatus is preferably located as close as possible to the distal end of the housing so that the sensed orientation of the housing will be as close as possible to the distal end of the borehole during operation of the device. The housing orientation sensor apparatus is preferably contained in or associated with an at-bit-inclination (ABI) insert located inside the housing.
The drilling direction control device may also be further comprised of a deflection assembly orientation sensor apparatus associated with the deflection assembly for sensing the orientation of the deflection mechanism (and thus the orientation of the bend in the drilling shaft). Such a deflection assembly orientation sensor apparatus may provide for sensing directly the orientation of the deflection mechanism in one, two or three dimensions relative to gravity and/or the earth""s magnetic field, in which case the deflection assembly orientation sensor apparatus may possibly eliminate the need for the housing orientation sensor apparatus.
Preferably, however the deflection assembly orientation sensor apparatus senses the orientation of the deflection mechanism relative to the housing and may be comprised of any apparatus which is capable of providing this sensing function and the desired accuracy in sensing.
Alternatively, the deflection assembly may be designed to be fixed relative to the housing so that the bend in the drilling shaft is always located at a known orientation relative to the housing (i.e., at a xe2x80x9ctheoretical high sidexe2x80x9d). In this case, the orientation of the bend in the drilling shaft will be determinable from the orientation of the housing and only one of a housing orientation sensor apparatus and a deflection assembly orientation sensor apparatus will be required.
Embodiments of suitable housing orientation sensor apparatus and deflection assembly orientation sensor apparatus are described in U.S. Pat. No. 6,244,361 B1.
A preferred embodiment of housing orientation sensor apparatus which could also be adapted for use as a deflection assembly orientation sensor apparatus and which is not described in U.S. Pat. No. 6,244,361 B1 senses the orientation of the apparatus relative to gravity.
In the preferred embodiment of housing orientation sensor apparatus, the apparatus is comprised of:
(a) a housing reference indicator which is fixedly connected with the housing at a housing reference position;
(b) a circular track surrounding the drilling shaft, which circular track houses a metallic gravity reference indicator which moves freely about the circular track in response to gravity, for providing a gravity reference position;
(c) a proximity assembly associated with and rotatable with the drilling shaft, which proximity assembly includes a housing reference sensor and a gravity reference sensor, wherein the housing reference sensor and the gravity reference sensor have a fixed proximity to each other.
In operation, the proximity assembly rotates as the drilling shaft rotates. As the housing reference sensor passes the housing reference indicator it will sense the housing reference indicator. Similarly, as the gravity reference sensor passes the gravity reference indicator it will sense the gravity reference indicator. Due to the known proximity between the housing reference sensor and the gravity reference sensor, the orientation of the housing relative to gravity can be determined from the sensed data.
The housing reference indicator may be comprised of any structure or apparatus which is compatible with the housing reference sensor. In the preferred embodiment the housing reference indicator is comprised of one or more magnets and the housing reference sensor is comprised of one or more Hall Effect sensors.
The gravity reference indicator may be comprised of any structure or apparatus which will move about the circular track in response to gravity and which can be sensed by the gravity reference sensor. In the preferred embodiment the gravity reference indicator is comprised of a movable metallic weight and the gravity reference sensor is comprised of a magnetic proximity sensor which is capable of sensing metal. Most preferably the gravity reference indicator is comprised of a metallic ball which is free to roll about the circular track.
The drilling direction control device may be further comprised of a housing locking assembly for selectively engaging the housing with the drilling shaft so that they rotate together. This feature is advantageous for applying torque to the housing to dislodge it from a wellbore in which it has become stuck.
The housing locking assembly may be comprised of any structure or apparatus which is capable of engaging the drilling shaft with the housing so that they rotate together. Preferably the housing locking assembly may be selectively actuated both to engage and disengage the drilling shaft and the housing. Alternatively, the housing locking assembly may be actuatable only to engage the drilling shaft and the housing so that the drilling direction control device must be removed from the wellbore in order to disengage the drilling shaft and the housing.
Preferably the housing locking assembly is comprised of a housing locking mechanism for engaging the drilling shaft with the housing and a housing locking actuator for actuating the housing locking mechanism.
The housing locking mechanism may be comprised of any structure or apparatus which is capable of engaging the drilling shaft and the housing such that they will rotate together. Preferably the housing locking mechanism is comprised of a locking member which is actuated to engage both the drilling shaft and the housing. Preferably the housing locking mechanism is longitudinally movable between positions where the drilling shaft and the housing are engaged and disengaged.
The housing locking actuator may be comprised of any structure or apparatus which is capable of actuating the housing locking mechanism. Preferably the housing locking actuator moves longitudinally in order to actuate the housing locking mechanism. Preferably longitudinal movement of the housing locking actuator results in longitudinal movement of the housing locking mechanism and thus actuation of the housing locking assembly.
In a preferred embodiment of housing locking assembly, the housing locking mechanism is comprised of a longitudinally movable locking sleeve and the housing locking actuator is comprised of a longitudinally movable locking actuator member.
In the preferred embodiment of housing locking assembly, the housing locking mechanism is further comprised of complementary engagement surfaces on each of the drilling shaft, the housing and the locking sleeve so that when the locking sleeve is actuated to engage the drilling shaft and the housing, the engagement surfaces on each of the drilling shaft, the housing and the locking sleeve are brought into engagement.
The complementary engagement surfaces may be comprised of any suitable surface which will provide the necessary engagement function. Preferably the complementary engagement surfaces are comprised of splines, but may also be comprised of a non-circular cross-sectional shape of the drilling shaft, housing and locking sleeve, such as a square or octagonal cross-sectional shape.
In the preferred embodiment of housing locking mechanism, the housing locking actuator is preferably further comprised of a power source. The power source may be comprised of the flow of drilling fluid through the drilling direction control device. Preferably, however, the housing locking actuator is comprised of an independent power source, such as a pump, a motor, or a pump/motor combination. Preferably the power source is comprised of a hydraulic system. Preferably the hydraulic system includes a reciprocating hydraulic piston in a cylinder. Preferably the hydraulic system further comprises a hydraulic pump for supplying hydraulic fluid to the cylinder. The hydraulic pump may be powered by any suitable motor or device. Preferably the hydraulic pump is powered by the rotation of the drilling shaft. Preferably the hydraulic pump is comprised of an annular pump such as a gear pump.
Preferably the hydraulic system is double acting so that the housing locking assembly can be actuated both to engage and disengage the drilling shaft and the housing.
A single power source may be provided as the power source for each of the deflection assembly, the indexing assembly and the housing locking assembly. Alternatively, one or each of the assemblies may be provided with its own dedicated power source.
Furthermore, a single actuator may be provided as a deflection actuator, an indexing actuator and a housing locking actuator. Alternatively, one or each of the assemblies may be provided with its own dedicated actuator.